This invention relates to optical panels and, in particular, to novel optical panels having superior environment resisting properties.
A conventional liquid crystal display device provides a digital display and includes a liquid crystal panel formed from two opposed substrates with a normally transparent liquid crystal material sealed between the substrates. Transparent electrodes are selectively disposed on the inner surface of each substrate in character forming segments with leads extending to the edges of the display. A voltage applied between opposed electrode segments alters the orderly arrangement of the molecules in the liquid crystal material to render the portion between the electrodes visually distinguishable from the remainder of the liquid crystal material.
In these conventional devices, it is desirable that the electrical resistance of all conductive material in the optical panel, i.e. each electrode terminal portion, remain constant. However, problems often arise because the electrical resistance of an electrode increases when the electrode is formed in a humid environment. Electrical resistance of the electrode also increases when the electrode is connected to the circuit substrate using electrically conductive rubber, or the like. Additionally, a terminal portion of an electrode can break as a result of electrolytic corrosion. Electrolytic corrosion can be measured in a test of current-conduction/moisture resistant properties of the liquid crystal display. Furthermore, when current conduction or electrical conduction continues through an optical path in an environment in which humidity changes significantly, disconnection can occur at a terminal portion of an electrode. Disconnection results, for example, from atmospheric moisture that causes the electrodes to become wet with dew or, alternatively, from electrolytic corrosion.
Accordingly, it is desirable to provide a novel optical panel and method of forming electrodes in that panel which overcome the disadvantages inherent in prior art optical panels.